using a function as an argument

[dsmey]

Hi all,

I'm trying to create a simple function in MS Visual Studio which would take a function and a range of values, divide that range into 500 equal steps, and barf out the results to a CLR richTextBox.

The function looks like this:

void Form1::Range(double from, double to, double f(double))
{
	for (int i = 0; i < 501; i++)
		{
		double x = (double)from + (to - from) * ((double)i / 500);
		double result = f(x);
		richTextBox7->AppendText(x.ToString() + "\t" + result.ToString());
		double ratio = (double)i/500.0;
		}
}

And when I call it I say this:

Range (0, 5, specweight);

Here's the function I'm passing as an argument (for now).

double Form1::specweight(double fkhz) {
	double expr;
	expr = fkhz/0.7-0.7/fkhz;
	return(1.0/sqrt(1.0+0.07*expr*expr));

}

Soooo, when I call it as above, Visual Studio says "function call missing argument list; use '&Pitch2Gui_Port3::Form1::specweight' to create a pointer to member"

If I call it like

Range (0, 5, specweight());

it complains that specweight "does not have 0 arguments"

If I call it like

Range (0, 5, specweight(double))

it says 'double' should be preceded by ')'

I could have sworn this worked in a C context (with the first method of calling it.) Maybe the difference is that these are member functions of Form1?

I've tried changing the argument to a pointer to function but can't get that to work either. Any tips?

[Narue]

There's a rather large difference between pointers to functions and pointers to instance member functions. The latter is actually an offset rather than a true pointer, so the two are not interchangeable.

http://www.parashift.com/c++-faq-lite/pointers-to-members.html